#!/usr/bin/env python
# -*- coding: utf-8 -*-
#===============================================================================
# Copyright 2011 zod.yslin
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# 
# Author: zod.yslin
# Email: 
# File Name: override.py
# Description: 
#   子類別也可依需要改寫 (override) 父類別的方法，這是說子類別需要用到與父類別
#   具有相同名稱的方法，但是子類別需要的功能有所修改、擴充或增加，因此當子類別
#   裡頭定義與父類別相同名稱的方法時，就會改寫父類別的方法。經過改寫，子類別的
#   方法完全屬於子類別所有
# Edit History: 
#   2011-08-10    File created.
#===============================================================================
class A(object):
    def m(self): print "save A's data"
class B(A):
    def m(self): print "save B's data"; super(B, self).m()
class C(A):
    def m(self): print "save C's data"; super(C, self).m()
class D(B, C):
    def m(self): print "save D's data"; super(D, self).m()

a = A()
a.m()
b = B()
b.m()

class Demo(object):
    
    __x = 0  # the instance of Demo subclass
 
    def __init__(self, i):
        self.__i = i
        Demo.__x += 1
     
    def __str__(self):
        return str(self.__i)
          
    def hello(self):
        print("hello " + self.__str__())
     
    @classmethod
    def getX(cls):
        return cls.__x
 
class SubDemo(Demo):
    def __init__(self, i, j):
        super(SubDemo, self).__init__(i)
        self.__j = j
     
    def __str__(self):
        """
        override Demo's method
        """
        return super(SubDemo, self).__str__() + "+subdemo+" + str(self.__j)
 
 
a = SubDemo(12, 34)
a.hello()
print("a.__x =", a.getX())
b = SubDemo(56, 78)
b.hello()
print("b.__x =", b.getX())
print("a.__x =", a.getX())
print("b.__x =", b.getX())

